High definition television (HDTV) is now being introduced. One aspect is the transmission system known as the Grand Alliance Advanced Television (ATV) system. The transmission system employed is also known as the 8 vestigial sideband (8-VSB) digital transmission system. The ATV VSB transmission system is known and need not be described in detail. By way of background, the 8-VSB system may operate in a broadcast mode with 8-level symbols (3 bits per symbol). Before transmission, data are received serially and randomized, forward-error-corrected (FEC) using a Reed-Solomon coding technique, interleaved and trellis coded. The format for this Transmission Layer signal is a data frame which includes synchronization signals.
A data frame for the Transmission Layer 8-VSB system includes two fields of 312 segments and two field synchronization segments, each of which are 832 symbols long. The first four symbols in each segment are segment synchronization symbols. Subsequent segments convey data formatted in the manner discussed above (randomized and coded). The data segments include the FEC codes. In the 8-VSB format, the field synchronization segments are placed at the beginning of each field (e.g., the first and 314th segments of a 626 segment frame).
The ATSC A/110B standard requires the precise measurement of the transmitter and antenna system delay (TAD), which is defined as the time delay from arrival of the cadence sync at the input of the conventional 8 VSB data processing subsystem until transmission of the start of the corresponding data frame sync data segment. The A/110 standard does not provide guidance as to how to physically measure this delay.
The ATSC standard is described in a document A/53 dated Apr. 12, 1995 and Sep. 16, 1995. That document is herein incorporated by reference. Additionally, the prior art includes U.S. Pat. Nos. 6,351,281; 6,590,881; and 4,805,189. These patents do not suggest the subject invention. The first of these patents (U.S. Pat. No. 6,351,281) utilizes a special code on the track signal in order to recognize such signal and ascertain any delays associated therewith. The second patent (U.S. Pat. No. 6,590,881) interrupts its transmissions on all sections for a short interval during which it determines the time of arrival of signals from other base stations. The third patent (U.S. Pat. No. 4,805,189) introduces the use of a matched filter for time measurement.
The prior art also includes U.S. Pat. No. 5,751,347. This last patent, while similar, requires a special receiver for measuring the time.